Commonway
Version V. 2026.09.26

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Grade-Separated Interchange

INT-GSI-10
Situational / Discouraged Intersections & Crossings

Grade-Separated Interchange

An interchange carrying conflicting movements on separate vertical levels, connected by ramps, eliminating at-grade conflict entirely. Freeway-scale only.

Related Media

The items below come from outside the Commonway System, external videos, podcasts, and articles related to this page's topic, not part of the guidebook itself.

Roads don't have to be FAT to be FAST Aligned

Roads don't have to be FAT to be FAST

Road Guy Rob

Explains the interrupted-flow/platooning physics behind signalized-arterial congestion, then covers Carmel's Keystone Parkway conversion to a limited-access road using compact elevated roundabout interchanges instead of a full diamond interchange.

(opens in new tab)

Typical at: Undeveloped Rural Suburban

Compact and Urban are edge cases. Core is an unlikely pairing.

#Design notes

This is an acknowledged fallback for genuinely Freeway-scale volume or speed beyond what even a turbo-roundabout can manage, not a general-purpose alternative to the Commonway System's roundabout-first intersection philosophy. It stays confined to the density range where full Freeway-scale roads themselves are realistic.1

Default (Freeway) (FRE-DEF-01) (reciprocal link to the Freeway-scale pattern this connects into), Turbo-Roundabout (INT-TRB-02) (explicitly named on this page as the tier just below it), Displaced Left-Turn (INT-DLT-14) (the faster, lower-cost alternative often chosen over this pattern at high-volume urban and suburban intersections)

#References

  1. Legal / regulatory American Association of State Highway and Transportation Officials, A Policy on Geometric Design of Highways and Streets.(opens in new tab)

Suggest changes to this page (opens in new tab) Text-only version Last updated September 10, 2026

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